The HiLo Vario

The HiLo Vario

A couple of years ago, on a particularly thermic flight near my home in Central Scotland, I was flying with two vario’s. I had a standard vario mounted on my harness and another one running as an app on an old smart phone in my pocket.

As I went up and down through multiple thermals (I was only just over a year into the sport at the time) the noise from my two devices was, to say the least, a stressful interruption to my concentration.

As I tried to remain in control, I then had a 50% asymmetric collapse as the varios continued to scream in my ear adding to my, already, flustered state.

It was at this point that I wondered, Is this how free flight is meant to be?? Surely the experience of flying the hills and mountains should be peaceful and calm like the birds.

Eventually, after some effort, I landed and breathed a sign of relief. Having been bleeped and blooped at for half an hour I suddenly thought: “Surely someone has created a silent vario?”.

An Idea is Spawned

An early prototype of the HiLo Vario

Apparently no one had invented a silent vario. However, from what I know about elementary electronics I knew that such a device could be built at home for very little cost.

It’s basically just a CPU, a barometric pressure sensor and a light cluster of some sort. There is a technology called “Arduino” which is a small development board that can be easily programmed from a PC by USB cable.

So over the next few weeks I went to work creating a “proof of concept” design with cheap parts bought on ebay.

Plenty of trial and error then followed, but with the help of experienced experts on the Arduino Forum, I eventually had a working model.


Components used to build the HiLo Vario

The components used in my design are as shown below:

  • Arduino Pro Mini development board. This is the heart of the system that carries out all the computational work.
  • The barometric pressure sensor is an MS5611 mounted on a GY-63 board. This sensor has an accuracy of 10cm. Easily enough for a vario.
  • The power comes from a 400mAh Lithium Polymer battery. This is “fed” through a Powerboost 500 providing a 5v line in to power the components
  • The LED cluster is a NeoPixel Stick – 8 x WS2812 5050, including a 100 micro Farad capacitor and a 500 Ohm resistor on the data line.
  • The green custom Printed Circuit board was one I had designed for me by an electronics engineer I found on the site and did the design for an amazing £8!
  • The latching switch and rubber button were found on ebay and the simply allow the Powerboost 500 charger to be switched on and off.

Arduino Code

The code in the Arduino is very basic C code and relatively easy to learn. I will, in time, put the code on to and let people comment and review it once I get the device to a completed state, but I’m still making changes and upgrades at present.

So I designed the vario to check changes in the pressure every half second and then process the response to the neopixels. Many other vario’s check the pressure up to 50 times a second, but for testing I felt half a second was sufficient. Having flown the vario with this time interval many times I am confident that it gives me reasonable feedback.

On power up, the HiLo will run a short demo of the green and red lights just to prove that it’s working and give a little feedback to the user. In truth, the Arduino actually boots up in about a second.

3D Printed Case

2 piece 3D printed case

After I developed the first “proof of concept” model, I quickly realised that to get this on to a paraglider for testing I would need to create an appropriate case.

I decided to invest in a 3D printer and design the case from scratch. I purchased a Creality Ender 3 Pro for about £250 and I was not disappointed! This printer is a fantastic entry level machine and capable of great quality prints once you’ve set it up correctly and understand the basics.

The design of the case was done using Blender. Blender is a 3d graphics and animation application mainly used for CGI cartoons, however, it is equally useful for creating engineering designs for 3d printing. No doubt some engineers will disagree on this, but Blender is free, so it worked for me!

In-Flight Tests

Prior to taking the device into the air, I decided it was safer to test it in my car.

So I spent some time driving around hilly roads near my home with it mounted on my dashboard and the results were very encouraging. You can easily simulate the flight path of a paragliding in a thermal by driving uphill at about 20mph.

Eventually I mounted the HiLo Vario on to my flight deck and, to my absolute delight, it worked perfectly! Each green LED indicates a 0.5 m/sec climb, and conversely every red LED shows 0.5m/sec sink.

The HiLo Vario is designed to be fixed to a riser just above the carabiner. I had designed it this way so that the LED’s are visible in your peripheral vision but not distracting.

You can have up to 8 green LED’s showing a climb 4m/sec.

Other conventional vario’s will give you a good indication of climb and fall, but none will show you your actual climb rate to the nearest 0.5m/sec.

Future Development

At this time I have only 2 working demos of the HiLo vario but I use one as my primary vario on all flights. I plan to make others and improve the design to the point where I can reproduce them quickly.

As for creating a full production model? Time will tell!

There’s a few engineering, safety and Legal hoops to jump through before I start thinking about making these available to other pilots. And then there’s the whole Deaf Pilot market, some of whom have already contacted me on social media showing genuine interest.

It may just be easier to make the whole project “Open Source” and let people make their own vario and collaborate ideas, so for now I’m just happy welcoming comments and feedback!

Anyone can contact me on Instagram at

and also on youtube at

or on email at


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